Method and apparatus for suppressing the noise of an aircraft jet engine

ABSTRACT

A thrust housing is mounted on an aircraft jet engine nacelle and has a plurality of nozzles at the aft end thereof. A cowling is fitted in spaced relation around the thrust housing and at its aft end is formed with a plurality of ejector tubes which are respectively disposed in spaced relation around the nozzles of said thrust housing. The cowling is mounted on the nacelle so that it can be moved to a first position wherein the forward end of the cowling abuts the nacelle and atmospheric air flowing along the nacelle is excluded from the interior of the cowling, or to a second position wherein the forward end thereof is spaced from the nacelle and atmospheric air enters the interior of the cowling and flows out of the aforesaid ejector tubes in annular streams respectively surrounding exhaust gas streams discharged through the nozzles of the thrust housing.

United States Patent l 13,572,463

[72] Inventor RodneyEschenburg 3,139,153 6/1964 DeRemer 18l/33(.221) SanDiego, Cit. 3,393,518 7/1968 Bridge 18l/33 (.221)

[21] AppLNo. 818,594 3,495,682 2/1970 Treiber 181/60X [221 File d g n-19 6 FORElGN rm-zms [45] Patente ar.

Assignee RohrCorPoraion 1,200,477 6/1959 France 181/51 Chula Vista,Calif. Primary Examiner-Robert S. Ward, .lr.

[54] METHOD AND APPARATUS FOR SUPPRESSING THE NOISE OF AN AIRCRAFT JETENGINE [56] References Cited UNITED STATES PATENTS 2,648,192 8/1953 Lee181/33(.222)

Attorney-George E. Pearson ABSTRACT: A thrust housing is mounted onanaircraft jet engine nacelle and has a plurality of nozzles at the aftend thereof. A cowling is fitted in spaced relation around the thrusthousing and at its aft end is formed with a plurality of ejector tubeswhich are respectively disposed in spaced relation around the nozzles ofsaid thrust housing. The cowling is mounted on the nacelle so that itcan be moved to a first position wherein the forward end of the cowlingabuts the nacelle and atmospheric air flowing along the nacelle isexcluded from the interior of the cowling, or to a second positionwherein the forward end thereof is spaced from the nacelle andatmospheric air enters the interior of the cowling and flows out of theaforesaid ejector tubes in annular streams respectively surroundingexhaust gas streams discharged through the nozzles of the thrusthousing.

Patented Mm so, 1971 4 Sheets-Sheet 1 INVENTOR.

BY RODNEY ESCHENBURG QMQQMJ ATTORNEY Patented March 30, 1971 3,512,463

-4 Shuts-Sheet 2 F|G 2 I INVENTOR.

BY RODNEY ESCHENBURG EM 0; 9w!

ATTORNEY Patented March 30, 1971 I 3,572,463

4 Sheets-Sheet 5 FIG. 3

INVENTOR.

BY RODNEY ESCHENBURG SM Q W ATTORNEY Patentd March 30, 1971 3,572,463

4 Sheets-Sheet 4 FIG. 4

INVENTOR.

BY RODNEY ESCHENBURG 8MB. QM

ATTORNEY METHOD AND APPATUS FOR SUPPRESSING THE NOiSiE Ola" AN AHRQRAETJET ENGINE BACKGROUND OF THE INVENTION This invention relates tojet-propelled aircraft and more particularly to a method and apparatusfor suppressing the noise of such aircraft.

A considerable portion of the objectionable noise of jetpropelledairplanes is associated with the high velocity jet streams which issuefrom their engine nacelles. In accordance with this invention annularstreams of atmospheric air are caused to flow around a plurality of jetstreams issuing from each engine nacelle of a jet-propelled aircraft.These streams of atmospheric air effectively reduce the perceived noiselevel at ground level within an area lying under the flight path of theaircraft, without adversely affecting the operation of said aircraft.

SUMMARY OF THE INVENTION Apparatus in accordance with this inventionpreferably comprises a thrust housing the forward end of which isfixedly attached to the aft end of an aircraft jet engine pod or nacelleso that thrust gas discharged from the engine enclosed within the latterenters the interior of the housing. The aft end of the thrust housing isformed with multiple nozzles through which the thrust gas flows to theatmosphere in the form of separate jet streams. A plurality of elongatesupport members are fixedly connected at one end thereof to the aft endof the nacelle and project rearwardly from the latter in parallelrelation with the longitudinal axis of the thrust housing, the supportmembers being evenly spaced apart circumferentially of the nacelle.Mounted on the support members for movement axially thereof is a cowlinghaving the same general shape as the thrust housing. More specifically,the forward portion of the cowling is cylindrical and fits around theforward end of the thrust housing in concentric, spaced relationtherewith, and the aft end of the cowling branches into a plurality ofejector tubes each disposed in concentric, spaced relation around arespective one of the nozzles of the thrust housing. Screw-typeactuators are provided on the nacelle for driving the cowling between afirst position wherein the forward edge abuts the aft edge of thenacelle and second position wherein the same edges are spaced apart tothereby permit atmospheric air to flow into the interior of the cowlingand through the annular spaces between the ejector tubes thereof and thenozzles of the thrust housing.

OBJECTS OF THE INVENTION It is accordingly an object of this inventionto provide effective means for suppressing the noise of a jet-propelledaircraft at any selected time during its flight, or while the aircraftis on the ground.

Another object of the invention is to provide a method of suppressingthe noise of a jet engine of an aircraft and also improving the thrustof said engine during low speed flight of the aircraft while not causinga loss of thrust during cruise flight.

An additional object of the invention is to provide sound suppressionapparatus for an aircraft jet engine, which apparatus is simple inconstruction and arrangement and thus economical to manufacture, operateand maintain.

DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a pictorial representation of a preferred embodiment of theinvention, the drawing illustrating a portion of an aircraft jet enginenacelle on which components of the sound suppression apparatus aremounted;

FIG. 2 is an end elevation of the same embodiment, taken along the planerepresented by line 2-2 in FIG. 1 and in the direction indicated in thelatter drawing;

IFIG. 3 is a longitudinal section of the same embodiment,

taken along the plane represented by line 3-3 in FlG. 2 and in thedirection indicated in the latter drawing, the view showing a stowedposition of a cowling which constitutes a major component of saidembodiment; and

FIG. d is a longitudinal section of the same embodiment, taken along thesame plane as in FIG. 3 and showing the aforesaid cowling in a deployedor operative position thereof.

Throughout the drawings and the following specification, the samenumbers refer to the same parts.

DETAILED DESCRIPTION In the accompanying drawings the number 10generally designated a nacelle which encloses an aircraft jet engine inconventional manner. An annular rib 12 (see FIGS. 3 and 4) is fixedlyconnected at the outer, flanged edge thereof to the outer wall 14 of thenacelle, and at the inner edge thereof is connected to the aft end ofthe tailpipe 16 of the aforesaid jet engine. The forward edge of athrust housing, generally designated by the number 18, is fixedly joinedto the aft edge of tailpipe 16 and includes a substantially cylindricalforward portion 20 and a plurality of tubular nozzles 22 which arejoined together at their forward ends by wall sections 24. As can beseen in FIG. 2, one of the nozzles is coaxial with the longitudinal axisof nacelle l0 and the other nozzles are arranged in two sets whichencircle the coaxial nozzle.

Three tubular support members 26A26C are fixedly attached at one endthereof to the rear side of rib l2 and project from the aft end ofnacelle 10. The support members are evenly spaced apartcircumferentially of rib l2 and have a square cross section, and theirlongitudinal axes are parallel with the longitudinal axis of thenacelle. -A cowling, generally designated in the drawings by the number28, is formed with a conical forward portion having double walls 30, 32,and with a plurality of tubular ejectors 34 which are integrally joinedto said forward portion. More particularly, inner wall 32 of cowling 28is spaced from the forward portion 20 of thrust housing 18 so as toprovide an annular gap therebetween, and ejectors 34 of the cowling arerespectively disposed around nozzles 22 and spaced therefrom to provideannular gaps therebetween. Mounting tubes 36A36C are fixedly positionedin apertures in walls 30 and 32 of the cowling and slidably engagesupport members 26A-26C, respectively, to thereby mount said cowling onsaid support members for movement axially thereof. Channels 37 (seeFIG. 1) are formed in cowling 28 to provide clearance for supportmembers 26A-26C. Rings 38, 40 are respectively fixedly secured to anddisposed between the aft ends of ejectors 34, and another ring 42 islikewise fixedly secured to and disposed between the aft ends of wall 32and tubes 36A36C, these rings being provided to increase the rigidity ofthe cowling.

Mounted on the rear side of rib R2 are three drive motors 44A-MC,whichmay be of any suitable type and which are connected by a rotatablecable 46 so that screws ASA-48C associated therewith can be rotatedsimultaneously at the same angular velocity and'in the same direction.The drive motors are respectively located between support members26A26C, and their screws 48A-48C extend through apertures in wall 32 ofcowling 28 and are respectively engaged within threaded apertures inthree lugs 50A50C which are fixedly mounted between said wall 32 andwall 30 of said cowling adjacent the forward end of the latter. Channels52 (see FIG. 1) are formed in cowling 28 aft of lugs 50A-0C to provideclearance for screws 48A-48C.

OPERATION When sound suppression is not required for an aircraftequipped with apparatus in accordance with this invention (such asduring high altitude flight), cowling 23 is in a first position whereinits forward end matingly abuts the aft end of nacelle 10, as illustratedin FIGS. l and 3. To suppress the noise associated with the jet streamsissuing from nozzles 22 of As illustrated by the double-headed arrows inthe last-mentioned drawing, atmospheric air then flows through theannular gap between the aft edge of nacelle l and the forward end ofcowling 28 and into the interior of the latter. It can be seen in thesame drawing that the aft ends of nozzles 22 of thrust housing 18 areadjacent the forward ends of ejector tubes 34 of cowling 28 when thelatter is in its deployed position. In FIG. single-headed arrowsrepresent the flow of thrust gas which flows from the jet enginecontained in nacelle through nozzles 22 of thrust housing 18. A portionof the air which enters the forward end of cowling 28 flows through theannular gaps between the outermost nozzles 22 and the ejector tubes 34surrounding these nozzles. A portion of the air also flows through thespaces between noules 22 toward the center of cowling 28 and issues fromthe latter through the annular gaps between the innermost nozzles andejector tubes associated therewith. Hence the jet streams issuing fromall of the nozzles 22 are surrounded by annular streams of air at theejector tubes 34, which suppresses the noise of said jet streams whenthey reach the atmosphere aft of said ejector tubes. 0bviously cowling28 can readily be returned to its stowed position against nacelle 10when suppression of the noise of the aforesaid jet streams is no longerrequired.

Atmospheric air which is admitted into cowling 28 not only suppressesthe noise of the jet engine associated therewith but also augments itsthrust. It will also be obvious that motors 44A-44C can be operated tovary the spacing between the aft end of nacelle 10 and the forward endof cowling 28 when the cowling is deployed. Thus the amount ofatmospheric air admitted into the cowling can be controlled to optimizethrust augmentation as the speed of the aircraft increases. For staticthrust the opening for atmospheric air flow will be maximum; for lowspeed flight, less air flow will be required; for climb, still less airflow; and for high speed flight the cowling will be closed against theaft end of nacelle 10.

Although the invention has been described with reference to a particularembodiment of the same, it should not be considered to be limitedthereto for various modifications could be made therein by one havingordinary skill in the art without departing from the spirit and scope ofthe invention as defined in the following claims.

I claim:

1. Jet engine apparatus comprising:

a nacelle enclosing a jet engine;

a thrust housing the forward portion of which receives exhaust gas fromsaid jet engine and the aft portion of which defines a plurality ofnozzles from which said exhaust gas is discharged;

a cowling surrounding said thrust housing and formed with a plurality ofejector tubes respectively disposed in spaced relation around saidnozzles; and

means for selectively admitting atmospheric air into and excluding thesame from the interior of said cowling.

2. Jet engine apparatus comprising:

a nacelle enclosing a jet engine;

a thrust housing the forward portion of which receives exhaust gas fromsaid jet engine and the aft portion of which defines a plurality ofnozzles from which said thrust gas is discharged;

a cowling surrounding said thrust housing, the forward end of saidcowling being annular and adapted to matingly abut the aft end of saidnacelle and the aft portion thereof defining a plurality of ejectortubes respectively disposed in spaced relation around said nozzles; and

means for moving said cowling axially of said nacelle between a firstposition wherein the forward end of said cowling abuts the aft end ofsaid nacelle and a second position wherein the forward end of saidcowling is spaced rearwardly of the aft end of said nacelle, wherebyatmospheric air can be selectively admitted into and excluded from theinterior of said cowling. 3. Jet engine apparatus comprising:

a nacelle enclosing a jet engine;

a thrust housing the forward portion of which is attached to saidnacelle and the aft portion of which defines a plurality of nozzles, theforward end of said thrust housing communicating with the tailpipe ofsaid jet engine so that exhaust gas from the latter discharges throughsaid nozzles;

a plurality of elongate support members each of which is fixedlyattached at one end to the aft end of said nacelle and extendsrearwardly therefrom, said support members being spaced apart externallyand circumferentially of said thrust housing and disposed parallel tothe longitudinal axis thereof;

a cowling surrounding said thrust housing and mounted on said supportmembers for movement axially of said nacelle, the forward end of saidcowling being annular and adapted to matingly abut the aft end of saidnacelle and the aft portion thereof defining a plurality of ejectortubes respectively disposed in spaced relation around said thrustnozzles; and

means for moving said cowling axially of said support members between afirst position wherein the forward end of said cowling abuts the aft endof said nacelle and a second position wherein the forward end of saidcowling is spaced rearwardly of the aft end of said nacelle, wherebyatmospheric air can be selectively admitted into and excluded from theinterior of said cowling.

4. The apparatus defined in claim 3 wherein said means for moving saidcowling comprises at least one screw mounted at the aft end of saidnacelle for rotation about its own longitudinal axis and threadedlyengaged with said cowling, and means for selectively rotating said screwin opposite directions to thereby move said cowling axially thereof.

1. Jet engine apparatus comprising: a nacelle enclosing a jet engine; athrust housing the forward portion of which receives exhaust gas fromsaid jet engine and the Aft portion of which defines a plurality ofnozzles from which said exhaust gas is discharged; a cowling surroundingsaid thrust housing and formed with a plurality of ejector tubesrespectively disposed in spaced relation around said nozzles; and meansfor selectively admitting atmospheric air into and excluding the samefrom the interior of said cowling.
 2. Jet engine apparatus comprising: anacelle enclosing a jet engine; a thrust housing the forward portion ofwhich receives exhaust gas from said jet engine and the aft portion ofwhich defines a plurality of nozzles from which said thrust gas isdischarged; a cowling surrounding said thrust housing, the forward endof said cowling being annular and adapted to matingly abut the aft endof said nacelle and the aft portion thereof defining a plurality ofejector tubes respectively disposed in spaced relation around saidnozzles; and means for moving said cowling axially of said nacellebetween a first position wherein the forward end of said cowling abutsthe aft end of said nacelle and a second position wherein the forwardend of said cowling is spaced rearwardly of the aft end of said nacelle,whereby atmospheric air can be selectively admitted into and excludedfrom the interior of said cowling.
 3. Jet engine apparatus comprising: anacelle enclosing a jet engine; a thrust housing the forward portion ofwhich is attached to said nacelle and the aft portion of which defines aplurality of nozzles, the forward end of said thrust housingcommunicating with the tailpipe of said jet engine so that exhaust gasfrom the latter discharges through said nozzles; a plurality of elongatesupport members each of which is fixedly attached at one end to the aftend of said nacelle and extends rearwardly therefrom, said supportmembers being spaced apart externally and circumferentially of saidthrust housing and disposed parallel to the longitudinal axis thereof; acowling surrounding said thrust housing and mounted on said supportmembers for movement axially of said nacelle, the forward end of saidcowling being annular and adapted to matingly abut the aft end of saidnacelle and the aft portion thereof defining a plurality of ejectortubes respectively disposed in spaced relation around said thrustnozzles; and means for moving said cowling axially of said supportmembers between a first position wherein the forward end of said cowlingabuts the aft end of said nacelle and a second position wherein theforward end of said cowling is spaced rearwardly of the aft end of saidnacelle, whereby atmospheric air can be selectively admitted into andexcluded from the interior of said cowling.
 4. The apparatus defined inclaim 3 wherein said means for moving said cowling comprises at leastone screw mounted at the aft end of said nacelle for rotation about itsown longitudinal axis and threadedly engaged with said cowling, andmeans for selectively rotating said screw in opposite directions tothereby move said cowling axially thereof.